WEALDEN FORMATION. 
313 
the Middle and Lower Speeton, the Fig. 287. 
latter of which, with the same mineral 
characters and fossils as in Yorkshire, 
is also found in the little island of 
Heligoland. Yellow limestone, which 
I have myself seen near Neuchatel, in 
Switzerland, represents the Lower 
!N^eocomian at Speeton. 
WEALDEN' FORMATION. Ammonites Noricus, Schloth. 
■n a .li 1 t 1 TT Lower Neocoinian, Speeton. 
Beneath the Atherheld clay or Up¬ 
per Neocomian of the S.E. of England, a fresh-water forma¬ 
tion is found, called the Wealden, which, although it oc¬ 
cupies a small horizontal area in Europe, as compared to 
the White Chalk and the marine Neocoinian beds, is nev¬ 
ertheless of great geological interest, since the imbedded 
remains give us some insight into the nature of the ter¬ 
restrial fauna and flora of the Lower Cretaceous epoch. 
The name of Wealden was given to this group because 
it was first studied in parts of Kent, Surrey, and Sussex, 
called the Weald; and ^ve are indebted to Dr. Mantell 
for having shown, in 1822, in his “Geology of Sussex,” 
that the whole group was of fluviatile origin. In proof of 
this he called attention to the entire absence of Ammonites, 
Belemnites, Brachiopoda, Echinodermata, Corals, and other 
marine fossils, so characteristic of the Cretaceous rocks above, 
and of the Oolitic strata below, and to the presence in the 
Weald of Paludinae, Melanise, Cyrense, and various fluviatile 
shells, as well as the bones of terrestrial reptiles and the 
trunks and leaves of land-plants. 
The evidence of so unexpected a fact as that of a dense 
mass of purely fresh-water origin underlying a deep-sea de¬ 
posit (a phenomenon with which we have since become fa¬ 
miliar) was received, at first, with no small doubt and incre¬ 
dulity. But the relative position of the beds is unequivocal; 
the Weald Clay being distinctly seen to pass beneath the 
Atherfield Clay in various parts of Surrey, Kent, and Sussex, 
and to reappear in the Isle of Wight at the base of the Cre¬ 
taceous series, being, no doubt, continuous far beneath the 
surface, as indicated by the dotted lines in the annexed dia¬ 
gram (Fig. 288). They are also found occupying the same 
relative position below the chalk in the peninsula of Pur- 
beck, Dorsetshire, where, as we shall see in the sequel, they 
repose on strata referable to the Upper Oolite. 
Weald Clay ,—The Upper division, or Weald Clay, is, in 
great part, of fresh-water origin, but in its highest portion 
14 
